# The Line 2x − Y + 6 = 0 Meets the Circle X2 + Y2 − 2y − 9 = 0 at a and B. Find the Equation of the Circle on Ab as Diameter. - Mathematics

The line 2x − y + 6 = 0 meets the circle x2 + y2 − 2y − 9 = 0 at A and B. Find the equation of the circle on AB as diameter.

#### Solution

The equation of the line can be rewritten as $x = \frac{y - 6}{2}$ .

Substituting the value of x in the equation of the circle, we get: $\left( \frac{y - 6}{2} \right)^2 + y^2 - 2y - 9 = 0$

$\Rightarrow \left( y - 6 \right)^2 + 4 y^2 - 8y - 36 = 0$
$\Rightarrow y^2 + 36 - 12y + 4 y^2 - 8y - 36 = 0$
$\Rightarrow 5 y^2 - 20y = 0$
$\Rightarrow y^2 - 4y = 0$
$\Rightarrow y\left( y - 4 \right) = 0$
$\Rightarrow y = 0, 4$

At y = 0, x = −3
At y = 4, x = −1
Therefore, the coordinates of A and B are

$\left( - 1, 4 \right) \text{and} \left( - 3, 0 \right)$

∴ Equation of the circle with AB as its diameter:

$\left( x + 1 \right)\left( x + 3 \right) + \left( y - 4 \right)\left( y - 0 \right) = 0$
$\Rightarrow x^2 + 4x + y^2 - 4y + 3 = 0$
Concept: Circle - Standard Equation of a Circle
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#### APPEARS IN

RD Sharma Class 11 Mathematics Textbook
Chapter 24 The circle
Exercise 24.3 | Q 10 | Page 37